A brand is a manufacturer who makes a product.
A supplier is a seller of that product.
Examples:
Apple makes their collection of different products, and they sell their own products. So Apple is both a brand and a supplier.
Sony makes TVs but does not allow its consumers to buy directly from them, instead, they have their users go through distribution. So Sony is a brand, but not a supplier
ADI does not make any products, but they do sell (distribute) a bunch of products they buy directly from these manufacturers. ADI is not a brand but a supplier.
Remember: A brand can also be a supplier of that product.
When navigating the catalog, remember that brands are where you will be searching for products manufactured by that brand. Suppliers will be who you buy the products from.
Make sure to take advantage of supplier-provided and managed costs, so you don't have to spend time adding the product costs and prices.